Mental Retardation

Mental Retardation

Mental Retardation

Mental retardation is a generalized neurodevelopment disorder characterised by significantly impaired intellectual and adaptive disorder present before age of 18yrs.

Mental retardation refers to significantly sub-average general intellectual functioning resulting in or associated with concurrent impairments in adaptive behaviour as manifested during the developmental period

This is characterised by below mental ability and average intelligence or lack of skills necessary for day to day living. People with mental retardation can and do learn new skills, but they learn them more slowly.

People with intellectual disability have the following limitations

  • Intellectual functioning also known as (intelligence quotient) IQ

This refers to a person’s ability to learn reason, make decisions, and solve problems.  Intelligence quotient is measured test of which the average is 100 and a person is considered intellectually disabled if the IQ is less than 70%

  • Adaptive behaviours

These are degrees with which the individual meets the standards of personal dependence and social responsibility expected of his age and cultural group.

These are skills necessary for day to day life such as being able to communicate effectively, interact with others and take care of one’s self.

Classification of Mental Retardation

Intelligence quotient is the ratio between mental age (MA) and chronological age (CA) where chronological age is determined from the date of birth and mental age is determined by the intelligence tests.

  • Mild mental retardation
  • Moderate mental retardation
  • Severe mental retardation
  • Profound
Mild mental retardation (educable)

These have IQ levels ranging from 50 to 69%. These children go undiagnosed until they reach school years. They are often slower to talk, walk and feed themselves as compared to other children. They can learn domestic and practical skills including reading and maths and achieve good independence in self-care like eating, washing, dressing etc. They can build social and job skills and can live on their own.


Moderate mental retardation (trainable)

These have IQ ranging from 35 to 49%.

Children with mild mental retardation show noticeable delays in developing speech and motor skills. Although they are unlikely to acquire useful academic skills, they can learn basic communication, some health and safety habits and other simple skills. They cannot learn how to read or do maths. Moderately retarded adults cannot live alone and need supervision throughout life but can do simple tasks and travel alone to familiar places.

Severe mental retardation (dependent retarded)

These have IQ ranging from 20 to 34%

This condition can be diagnosed as early as at birth or very soon after birth. By preschool age, they show delays in motor development and little or no ability to communicate. With good training, they can learn self-help skills such as how to feed or bath themselves. They usually learn to walk and gain basic understanding of speech as they get older.

Adults with severe mental retardation may be able to follow daily routines but need through supervision and to be kept in a protected environment.

Profound mental retardation (life support)

Only a few people with mental retardation have IQ below 20%.

This condition is diagnosed at birth and is associated with other medical problems which require nursing care. The children show delays in all aspects of development.

Most individuals are immobile, have limited ability to understand, are unable to care for themselves, have various neurological and physical disabilities, visual and hearing abilities are impaired and so many other associated disabilities.

Causes of Mental Retardation

Mental retardation is a complex action which may be caused by interaction of many factors and in 75% of patients, the cause is unknown.

Genetic factors

  • If one or both parents have mental retardation, chances that children develop this condition are high.
  • Sometimes mental retardation is caused by abnormalities of chromosomes rather than individual genes e.g. down syndrome where an individual has an extra chromosome in the cell.

Problems during pregnancy

  • Infections in pregnancy like TORCHES; toxoplasmosis, Rubella, Cytomegalovirus, Syphilis, herpes simplex.
  • Alcohol in pregnancy may cause mental retardation through Fetal Alcohol Syndrome FAS
  • Placental dysfunction like toxaemia of pregnancy, placenta previa, cord prolapse etc.
  • Some drugs like cocaine when taken in pregnancy may harm mental development of unborn child.
  • Maternal malnutrition
  • Exposure to radiations

Problems during birth (perinatal factors)

  • Prematurity
  • Very low birth weight
  • Instrumental delivery
  • Prolonged labour
  • Kernicterus
  • Birth asphyxia

Problems after birth (postnatal factors)

  • Lead or mercury poisoning
  • Severe malnutrition
  • Accidents that cause severe head injury
  • Diseases such as meningitis, encephalitis etc.
  • Untreated hypothyroidism
  • Brain tumours
  • Epilepsy

Environmental causes

  • Cultural deprivation
  • Low socio-economic status
  • Inadequate caretakers
  • Child abuse

Signs and symptoms of mental retardation

These vary greatly depending on the severity of the condition

  • IQ below 70%
  • Failure to achieve developmental milestones
  • Delay in oral language development
  • Deficit in memory skills
  • Difficult learning social roles
  • Difficult with problem solving skills
  • Decreased learning abilities or inabilities to meet education demands at school
  • Limited motor and communication skills
  • Visual and hearing impairments
  • Epilepsy always accompanies the problem
  • Require constant supervision
  • Neurological disorders are very common
  • Some may have psychotic or behavioural disorders
  • Self-care is a problem to these patients.


This can be made by

  1. IQ testing (MA/CA)X100
  2. Taking history from the parents or care giver
  3. Carrying out biochemical tests
  4. Physical examination
  5. Neurological examination
  6. Assessing developmental milestones
  7. Investigation
  • Urine and blood for metabolic disorders
  • Culture for biochemical studies
  • Amniocentesis in infant chromosomal disorders
  • Chorionic villi sampling
  • Hearing and speech evaluation
  • CT scan or MRI
  • Thyroid function tests when cretinism is suspected
  1. X-ray

Management of Mental Retardation

Majority of the mentally retarded children and adults are cared for at home and admission is only required because of incompetent parents, psychotic behaviours, stigmatisation etc.


  1. To enable the patient reach his or her maximum potential ability
  2. To ensure safety of the patient.
  • Mentally retarded children are admitted in hospitals or any other institution with schools that offer them training and education suitable to their abilities.
  • Physical training, recreation, and social activities also play a part in treatment regimen
  • Love, attention and care are one of the most required elements for these children
  • Written, verbal and pictorial forms of communication as well as gestures and demonstration are very helpful to ensure mutual understanding and improve treatment adherence
  • Programmes that maximise speech, language, cognition, psychomotor, social, self care and occupational skills have to be encouraged
  • The main stay of treatment is by developing a comprehensive management plan for the condition which includes multiple disciplines like special educators, language therapists, behavioural therapists, occupational therapists and community service providers that provide social support to affected families.
  • On-going evaluation for overlapping psychiatric disorders such as depression, bipolar disorder and ADHD
  • Neuroleptics such as haloperidol are given in cases of psychotic behaviour
  • Analgesics are required for management of pain especially in severe mental retardation.
  • Family therapy to help parents develop coping skills and deal with guilt and anger
  • Early intervention programs for children younger than age 3 with mental retardation
  • Provide day schooling to train the child in basic skills such as bathing and feeding
  • Vocational training
Prevention of mental retardation


  • Genetic counselling
  • Immunisation of maternal rubella
  • Adequate maternal nutrition
  • Family planning

During gestation

  • Adequate nutrition
  • Fetal monitoring
  • Protection from diseases
  • Avoidance of teratogenic substances like alcohol and exposure to radiations

At delivery

  • Delivery should be conducted in the hospital
  • Apgar scoring has to be done at 1 and 5 minutes after the birth of a child
  • Close monitoring of mother and child


  • Improved general medical care for children
  • Improved nutrition for children
  • Proper and early treatment for childhood infections
  • Immunisation of children according to immunisation schedule
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